148 
Simon, Ziemann 
The cumulative effect of such a process can be presented in a tone reproduction diagram. 
CCD's record light intensities in a linear way; hence they react quite differently to light intensities as do film and the human eye. 
Therefore, thought needs to be given to a suitable way of recording images digitised with an office scanner incorporating a linear 
CCD, such as the scanners of the type Agfa Horizon Plus an Arcus II; both have an optical resolution of 1200 ppi. The relative 
expensive Horizon allows images up to A3 size, the relative inexpensive Arcus up to A4 size. 
KanafSchwarz 
Mittelwert: 56.79 
Abweichung: 60.85 
ZentraKvert: 31 
Pixel: 110760 
Fig. 2: Original step tablet (a, top), scanned image(b, centre) 
and histogram of b (c, bottom) 
Dichte 
Fig. 3: Step-tablet densities versus obtained digital 
Fig. 4: Performance of the scanner 
Fig. 6: Presentation of the correction curve 
in FOTO LOOK 
Korrekturkurve 
Graustufen (Ausgabe) 
Sollwert 
Fig. 5: Derivation of a correction curve 
Fig. 7: Histogram of an image scanned using the 
correction curve from fig. 6